Yes it does but again, what is the goal here?
Holden wanted improved fuel economy and emission figures from a car that is a bit fat.
They achieved this and the result for them is a car that can compete in their traget market and therefore this will translate into more sales.
In the case here, any saving in terms of fuel economy will be countered the moment you take of from the lights a bit quicker and any performance increase will not be noticable.
Removing the spare makes no sense as the gains won't be noticable and the cost of a fine would outweight the savings found from improved fuel economy. That and the cost of the time spent waiting for a mate to bring a spare is something to consider.
And in terms if a titanium exhaust, again, negligible improvement in performance. Negligible savings in terms of fuel economy but the cost outlay would be substantial. And at the end of the day, its all about return on investment which is also referee to "bang for buck".
In both cases above, it simply does not make sense.
Weight retuction makes sense if the car is a performance car, its already at the limits of handling and engine performance but you are still looking for a fraction of a second here or there. And then we are talking proper, full in weight reduction that will compromise features and comfort but achieve gains per lap or at the end of the strip.
